The present invention is directed to apparatus and methods for making bags, and more particularly, concerns a vertical form, fill and seal machine and method for making recloseable, product-filled bags.
Vertical form, fill and seal machines and methods for making recloseable bags from a bag forming film and a separate plastic zipper element are described, for example, in U.S. Pat. Nos. 4,709,533, 4,874,257, and 4,894,975. The plastic zipper element is fed between the film edges and the film and zipper are joined by heated sealing bars. The thus formed and sealed tube is filled with product through the fill tube and cross-seals and cross-cutters complete the individual bags.
U.S. Pat. Nos. 4,869,048 and 5,054,270 describe vertical form, fill and seal machines which produce recloseable bags from a bag forming film having respective zipper profiles attached to each edge of the film.
Although the above described patents provide examples of vertical form, fill and seal apparatus and methods for forming recloseable bags, there is a need for an improved vertical form, fill and seal machine and method which not only forms recloseable, product-filled bags, but also which produces durable, substantially airtight bags at high speeds, which facilitates the production of different size bags, and/or readily accommodates the addition of different types and amounts of product.